System and method for producing methane from a methane hydrate formation

ABSTRACT

A system for producing Methane from a Methane Hydrate formation including a completion that is disposed through a Methane Hydrate formation. An inlet of the completion disposed in the Methane Hydrate formation; and a drain for water located in a direction proximate a direction of gravity relative to the Methane Hydrate formation and gravitationally beneath the Methane Hydrate formation. A method for producing methane from a Methane Hydrate formation

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of an earlier filing date from U.S.Provisional Application Ser. No. 62/334,752 filed May 11, 2016, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

Methane Hydrate exists in vast quantities throughout much of planetEarth. Methane can be liberated from Methane Hydrate if the temperatureand or pressure is adjusted to permit dissociation. In recent years,operators have been trying to find ways to economically produce methaneas an energy resource. Unfortunately problems have been encountered inconnection with configurations and methods designed to recover thisresource. One problem that is quite consistent is the reformation ofhydrate within the production system causing plugs to form. This ofcourse restricts or prevents production reducing viability of the well.The art has attempted to combat the problem by the addition of chemicalspecies such as Ethylene Glycol, Methanol or other hydrate inhibitors.While these work, they are costly and they are considered environmentalhazards thereby requiring additional processing, which only adds morecost to the operation.

Other efforts have included separating liquid water from the gas phasemethane. FIG. 1 illustrates a system that employed this concept.Unfortunately this method continued to suffer from hydrate reformationleaving the industry at a loss for achieving acceptable productionlevels. Chemicals have a host of issues surrounding their use andseparation didn't work. Referring to FIG. 1, the system for separatingwater from methane gas comprises a borehole 10 extending into a methanehydrate accumulation formation 12. A sand screen assembly 14 is disposedat the methane hydrate interval to allow fluids from the formation toenter the borehole and completion string 16. Uphole of the sand screenassembly 14 is an ESP assembly 16 comprising an ESP shroud 20,surrounding an ESP intake 22, an ESP gas separator 24, and an ESP pump26. A crossover 28 is used to swap the separated water and gaseousmethane for movement in the tubing-casing annulus 30 and tubing 32,respectively, to surface. The system was intended to work by drawingwater and sublimated methane from the formation 12 through screen 14,moving the fluid uphole to the OD of the shroud 20 and allowing liquidwater to spill over the uphole edge 34 of the shroud while the gascollected in chamber 36 is flowed into the crossover 28 and produced tosurface. As noted however, the system did not work and sufferedreformation of hydrates such that chemicals are needed to make the wellproduce efficiently over time, with all of the inherent drawbacks ofchemical use. The art then has been left searching for some other typeof solution to the problem of efficient production Methane from aMethane Hydrate formation.

The art would be highly receptive to a system and method for efficientproduction of Methane from a Methane Hydrate formation.

BRIEF DESCRIPTION

A system for producing Methane from a Methane Hydrate formationincluding a completion that is disposed through a Methane Hydrateformation; an inlet of the completion disposed in the Methane Hydrateformation; and a drain for water located in a direction proximate adirection of gravity relative to the Methane Hydrate formation andgravitationally beneath the Methane Hydrate formation.

A method for producing methane from a Methane Hydrate formation,including causing Methane Hydrate in a Methane Hydrate formation tochange phase; collecting liquid water in a direction proximate adirection of gravity as it enters a completion of a borehole; andcollecting free gas in a direction proximate a direction oppositegravity as it enters a completion of a borehole.

A method for producing Methane from a Methane Hydrate formationincluding passing water into a borehole in a direction that is proximatethe direction water will flow under the influence of gravity; passingMethane into the borehole in a direction that is proximate a directionagainst the direction of gravity; and managing the water collected to aselected location.

A production system for producing Methane from a Methane Hydrateformation, the system configured to dissociate the Methane Hydrate andmaintain separation of Methane gas and nongaseous material as it entersthe system and resides in the system.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is an illustration of a prior art system designed for Methaneproduction from a Methane Hydrate formation;

FIG. 2 is an illustration of a system and method for Methane productionfrom a Methane Hydrate formation as disclosed herein; and

FIG. 3 is an illustration similar to FIG. 2 but with a separate stringfor liquid disposed within the annulus of the production string.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring to FIG. 2, a novel configuration of wellbore components willsuccessfully meet the needs of the industry. Illustrated is a productionoperation 50 for a subsea Methane Hydrate formation. It is to beunderstood, however, that the system disclosed herein is not limited tosubsea operations but may be employed to produce Methane from MethaneHydrate formations anywhere such a formation exists. A production systemis defined as extending from a target formation to a processing systemthat processes produced raw fluids that may be local or remote from awellhead. Accordingly, while the illustrated operation 50 includes aplatform 52 at sea level 54 and a riser 56 extending to a wellhead 58 atthe seabed 60, these are not always a part of the system since thesystem is equally applicable to land borne operations. More important isthe description of the system beneath the seabed 60. A borehole 62extends to and through a Methane Hydrate formation 64. The boreholecomprises a completion that includes a production string 66 and an inletthat may be a sand screen assembly 68. The production string 66 includesan “inverted” ESP (Electric Submersible Pump) 69, meaning the ESP isconfigured to pump in a downhole direction as opposed to an upholedirection, positioned gravitationally beneath the formation 64.

It will be appreciated by one of ordinary skill in the art from thedrawing that as the Methane Hydrate formation 64 begins to dissociatefrom a solid to a nongaseous material that is predominantly liquid(water 70) and from a solid to a gas via sublimation (Methane 72) thegas will naturally migrate to a position away from the pull of gravityrelative to the water which will naturally migrate toward the pull ofgravity. Because conditions are specifically tailored to causedissociation at this location, dissociation necessarily will occur andwill result in a full separation of water and Methane. It will also beappreciated from FIG. 2 that the free water from the formation iscollected only into the lower portion of the borehole 62 somewhatsimilar to a household sink drain. The water will move down into thedrain 67 and feed the ESP 69, which as noted above is “inverted”. Asillustrated, the water 70 is being pumped by ESP 69 to a water disposalzone 74. The disposal zone 74 may be gravitationally beneath the MethaneHydrate formation as illustrated but also may be in a lateral borehole,or even pumped back to surface through another string that may be anentirely separate string in another borehole, a separate string 78within the same borehole (FIG. 3) or by using the annulus 80 around theproduction string 66 (FIG. 3 still serves by ignoring separate string78). It will be appreciated that FIG. 3 employs a flow conduit 82 thatextends from an ESP outlet 84, in a sealed manner, through packer 86uphole of a free gas inlet 88 to the production string 66. This willprovide access for water to the string 78 or the annulus 80 above packer86 without contacting the gas flow in the production string 66. Itshould be noted that in this embodiment the ESP does not discharge in adownhole direction but still is located gravitationally beneath theformation 64 such that the water drain still functions as in eachembodiment hereof.

The water 70 freed in the dissociation process is pure water and so canbe deposited underground, released into the sea, used to irrigate nearbycrops, collected in a receptacle of some sort (hold of a ship, largecontainer, etc.) and contained for use later, etc. The dissociated gasis also pure and hence the gas migrating into the borehole above thelevel of the water migrating into the borehole has no water associatedtherewith and cannot then reform hydrates in the production string. Thisis a significantly different result than the prior art and is surprisingto those of ordinary skill in the art since the art already has learnedthat separating the water and the gas is ineffective from the systemdescribed in the background section of this application. What heretoforethe art failed to understand is that it was not the idea of separatingwater from gas that was the failure but that the configuration designedto have that effect failed to achieve the goal, unbeknownst to the art.What actually occurs is that the action of the water and gas movingthrough the screen and up the borehole to the ESP shroud edge 34 at highvelocity causes a significant amount of entrainment of water in the gasflow and gas in the water flow. Accordingly, the system of FIG. 1 neverdid get the water and the gas separated and hence suffered fromreformation of hydrate when pressure and temperature conditions withinthe system became conducive to hydrate re-formation. Due to the lengthof a production system and the external changing conditions around aborehole and a riser (for a seabed located formation) it is extremelydifficult if not impossible to ensure conditions are never conducive tohydrate formation. Experience has shown us that it is not possible toreliably and economically control those conditions since the previousattempts (other than very expensive heating apparatus and chemicaladditive methodologies) have been unsuccessful. Practicing in accordancewith the present teaching however, substantially eliminates or reducesthe potential for hydrate formation to such an extent as to benegligible because the base materials necessary to hydrate formation(water and Methane) are not commingled at all in the completion system.More specifically, a production system for producing Methane from aMethane Hydrate formation, in accordance with the teachings hereof isconfigured to dissociation the Methane Hydrate and maintain separationof Methane gas and nongaseous material as it enters the system andresides in the system. It is in this way that hydrate reformation isavoided.

The method for producing Methane from a Methane Hydrate formationincludes passing water into a borehole in a direction that is proximatethe direction water will flow under the influence of gravity; passingMethane into the borehole in a direction that is proximate a directionagainst the direction of gravity; managing the water collected to aselected location and producing the Methane to a containment vessel thatmay be on a seabed, on ground, on a floating vessel such as shown at 52,etc. The passing of Methane may be passive or active. Draining the waterinto the borehole in a direction water will flow under gravity isillustrated in FIG. 2 where the water moves to a portion of the boreholegravitationally beneath the formation 64. It is then assisted by the ESPalthough it is possible that a particular formation could provide adestination for the water that it can achieve without the assistance ofthe pump and hence it is contemplated that the system and method mightnot require the ESP. The gas on the other hand does of course migrate ina direction different than the water does with respect to gravitybecause the density of the gas is so much less than the density of thewater. The gas is allowed to move into the completion and is ported tosurface or other containment vessel for further processing or use.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1

A system for producing Methane from a Methane Hydrate formationincluding a completion that is disposed through a Methane Hydrateformation; an inlet of the completion disposed in the Methane Hydrateformation; and a drain for water located in a direction proximate adirection of gravity relative to the Methane Hydrate formation andgravitationally beneath the Methane Hydrate formation.

Embodiment 2

The system in any of the preceding embodiments, further comprising apump disposed in the drain and configured to pump water.

Embodiment 3

The system in any of the preceding embodiments, wherein the pump isconnected to a flow conduit that reverses direction of the water andconveys the water to a separate pathway in the same borehole.

Embodiment 4

The system in any of the preceding embodiments, wherein the separatepathway is an annulus defined by a production string of the completion.

Embodiment 5

The system in any of the preceding embodiments, wherein the separatepathway is within the annulus and in a separate string.

Embodiment 6

The system in any of the preceding embodiments, wherein the pump is aninverted Electric Submersible Pump.

Embodiment 7

The system in any of the preceding embodiments, wherein the inlet is asand screen assembly.

Embodiment 8

The system in any of the preceding embodiments, wherein the drain isconnected to a water disposal zone.

Embodiment 9

The system in any of the preceding embodiments, wherein the waterdisposal zone is a formation.

Embodiment 10

The system in any of the preceding embodiments, wherein the waterdisposal zone is a lateral borehole.

Embodiment 11

The system in any of the preceding embodiments, wherein the waterdisposal zone is a container.

Embodiment 12

The system in any of the preceding embodiments, wherein the waterdisposal zone is a sea.

Embodiment 13

A method for producing methane from a Methane Hydrate formation,including causing Methane Hydrate in a Methane Hydrate formation tochange phase; collecting liquid water in a direction proximate adirection of gravity as it enters a completion of a borehole; andcollecting free gas in a direction proximate a direction oppositegravity as it enters a completion of a borehole.

Embodiment 14

A method for producing Methane from a Methane Hydrate formationincluding passing water into a borehole in a direction that is proximatethe direction water will flow under the influence of gravity; passingMethane into the borehole in a direction that is proximate a directionagainst the direction of gravity; and managing the water collected to aselected location.

Embodiment 15

The method in any of the preceding embodiments, further comprisingproducing the Methane to a containment vessel.

Embodiment 16

The method in any of the preceding embodiments, wherein the passingwater is drawing water using a pump configured to pump water in adirection other than a direction in which the Methane is passed.

Embodiment 17

The method in any of the preceding embodiments, wherein the passingMethane is passive.

Embodiment 18

The method in any of the preceding embodiments, wherein the passingMethane is active.

Embodiment 19

A production system for producing Methane from a Methane Hydrateformation, the system configured to dissociate the Methane Hydrate andmaintain separation of Methane gas and nongaseous material as it entersthe system and resides in the system.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Further, it should further be noted that the terms “first,”“second,” and the like herein do not denote any order, quantity, orimportance, but rather are used to distinguish one element from another.The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (e.g., itincludes the degree of error associated with measurement of theparticular quantity).

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited.

What is claimed is:
 1. A system for producing Methane from a MethaneHydrate formation comprising: a completion that is disposed through aMethane Hydrate formation; an inlet of the completion disposed in theMethane Hydrate formation; and a drain for water located in a directionproximate a direction of gravity relative to the Methane Hydrateformation and gravitationally beneath the Methane Hydrate formation. 2.The system as claimed in claim 1 further comprising a pump disposed inthe drain and configured to pump water.
 3. The system as claimed inclaim 2 wherein the pump is connected to a flow conduit that reversesdirection of the water and conveys the water to a separate pathway inthe same borehole.
 4. The system as claimed in claim 3 wherein theseparate pathway is an annulus defined by a production string of thecompletion.
 5. The system as claimed in claim 4 wherein the separatepathway is within the annulus and in a separate string.
 6. The system asclaimed in claim 1 wherein the pump is an inverted Electric SubmersiblePump.
 7. The system as claimed in claim 1 wherein the inlet is a sandscreen assembly.
 8. The system as claimed in claim 1 wherein the drainis connected to a water disposal zone.
 9. The system as claimed in claim8 wherein the water disposal zone is a formation.
 10. The system asclaimed in claim 8 wherein the water disposal zone is a lateralborehole.
 11. The system as claimed in claim 8 wherein the waterdisposal zone is a container.
 12. The system as claimed in claim 8wherein the water disposal zone is a sea.
 13. A method for producingmethane from a Methane Hydrate formation, comprising: causing MethaneHydrate in a Methane Hydrate formation to change phase; collectingliquid water in a direction proximate a direction of gravity as itenters a completion of a borehole; and collecting free gas in adirection proximate a direction opposite gravity as it enters acompletion of a borehole.
 14. A method for producing Methane from aMethane Hydrate formation comprising: passing water into a borehole in adirection that is proximate the direction water will flow under theinfluence of gravity; passing Methane into the borehole in a directionthat is proximate a direction against the direction of gravity; andmanaging the water collected to a selected location.
 15. The method asclaimed in claim 14 further comprising producing the Methane to acontainment vessel.
 16. The method as claimed in claim 14 wherein thepassing water is drawing water using a pump configured to pump water ina direction other than a direction in which the Methane is passed. 17.The method as claimed in claim 14 wherein the passing Methane ispassive.
 18. The method as claimed in claim 14 wherein the passingMethane is active.
 19. A production system for producing Methane from aMethane Hydrate formation, the system configured to dissociate theMethane Hydrate and maintain separation of Methane gas and nongaseousmaterial as it enters the system and resides in the system.